Hot flue gas leaving most industrial manufacturing facilities carries significant quantities of thermal energy which may be recovered for various applications including heating water for industrial use, or directly feeding flue gas into the tubes of heat exchanger coils or shell and tube elements for use in boilers, economizers and related apparatus. However, most bulk hot flue gas also carries significant quantities of particulate in the form of ash, silt, dust, metal particles and the like. The particulate in most hot combustion gases prevents economical and efficient use of the hot flue gas in heat exchange equipment, because it causes clogging of the equipment and/or reduces the heat transfer coefficient.
Particulate in flue gas typically fouls heat exchange equipment rapidly, requiring use of chemicals and/or significant equipment down-time for removing particulate build-up from heat exchange elements. The build-up of deposits in heat exchange elements resulting from particulate minimizes the available heat exchange area and significantly decreases the heat transfer coefficient of the elements. As a result, such heat exchange equipment must periodically be taken off-line and mechanically cleaned, involving disconnection and cleaning or replacement of heat exchange elements. Most de-fouling methods incur additional operating expenses in the form of man-hours, replacement elements, lost production time and/or the cost of chemical cleaning agents. The need to remove particulate from heat exchange elements typically further entails that such heat exchange equipment cannot be used continuously.
In addition, in many cases, particulate removal incurs further additional capital costs as a result of increased cost involved with baghouse equipment. Most baghouses cannot accept gas at temperatures over about 500.degree. F. As such, the hot flue gas is cooled by blending with large volumes of cool air to transfer the gas to the baghouse. This procedure increases the size of the baghouse piping and equipment to process such large volumes of air, thereby further increasing the capital cost of particulate removal.
There is a need in the art for reducing the temperature of industrial flue gas flows in order to reduce capital operating costs of removal of particulate. Further, there is a need for a continuous method for utilizing the high thermal potential of industrial hot flue gas flows to generate power for use in industrial facilities, which easily and economically removes particulate from heat exchange equipment without incurring unnecessary down-time, additional man-hours or chemical agents. There is also a need for an apparatus for use in a continuous process which fits economically in the available space of most industrial facilities, is easily transportable to industrial facilities having a source of hot flue gas, and which can be used in conjunction with available industrial plant water resources to generate steam to be converted to power for use throughout an industrial facility.